In-Line Carburizing

SyncroTherm is a heat treat process that is fully synchronized and integrated with soft and hard machining (All photos courtesy of ALD Vacuum Technologies).

By combining high-temperature, low pressure carburizing and high-pressure gas quenching, ALD Vacuum Technologies GmbH has integrated the case hardening process with the manufacturing line. Using a very compact piece of equipment, the company has provided a heat treat process known as SyncroTherm that is fully synchronized and integrated with soft and hard machining. The components are transported individually from each working-step to the next working-step following the "One-Piece-Flow" philosophy. A continuous product-flow is then generated with optimal synchronization of the manufacturing production line.

"We have proven that we can match a cycle-time from soft machining of 20 seconds or less with this piece of equipment," says Dr. Ing. Volker Heuer, Director R&D Vacuum Heat Treatment, ALD Vacuum Technologies GmbH. "ALD had some initial ideas on this concept ten years ago, but only since the GETPRO Congress at Hannover Messe in 2009 have we learned that there is a real customer demand for such a system. So, in mid-2009 we started to develop the concept."

The external handling system featured in the SyncroTherm places single parts on the workpiece carrier and transports it through the front opening in the quench chamber, which now serves as a loading chamber. The chamber is evacuated in order to remove unwanted oxygen. The telescopic loader, integrated in the treatment chamber, proceeds to place the workpiece carrier into a vacant hot zone. In the hot zone the strong radiant heat rapidly and homogeneously heats the parts to treatment temperature, followed by carburization.

According to the "One-Piece-Flow" principle, the heat treatment of large batches is converted to treatment of single components. The parts are charged in one layer on one workpiece carrier. The flat-panel radiators installed in top and bottom radiate the heat directly onto each part, heating the "2-D-charges" rapidly and homogeneously. The micro-alloyed steel parts are carburized at high temperatures above 1,000 degrees Celsius without undesired grain growth.

Advantages of the SyncroTherm process include quality improvements, less heat treat distortion and better carburizing uniformity.

ALD Vacuum Technologies is targeting the gear industry for the SyncroTherm system though potential applications can also be found in fuel-injection systems and the aerospace industry. "We have started to present this technology at international conferences (Ed's Note: One such presentation will be given at AGMA's 2011 Fall Technical Meeting). Since February 2011, we've had a prototype in our lab in Hanau, Germany that is ready for customer testing," Heuer says.

ALD-Holcroft, based in Wixom, Michigan, has partnered with ALD Vacuum Technologies for marketing efforts in the United States. "The most important market for us is the manufacturing of gear components for the car industry, so far mainly in Europe and Asia," Heuer says. "Other important markets for ALD heat treat are fuel-injection systems for cars and trucks, gear components for trucks, aerospace components and tools and dies."

So what are the advantages to the SyncroTherm concept? First, there's quality improvements thanks to the individual processes customized for each gear component. There's less heat treat distortion due to the single layer treatment (uniform heating, carburizing and quenching) and there's better carburizing uniformity, according to Heuer.

"The environmental benefits include no open flames, no hot walls (walls are water-cooled), no usage of oils and no detergents for oil removal. Cost benefits include reduced costs of logistics in the plant, reduced turnaround times (from up to five days to less than four hours) reduced efforts for quality management, cost reduction in hard machining due to reduced distortion and a space-saving manufacturing concept thanks to the compactness of the machine."

The external handling system featured in the SyncroTherm places single parts on the workpiece carrier and transports it through the front opening in the quench chamber.

The initial response to the SyncroTherm process has been very good and first test runs have generated positive feedback. And it fits nicely with other ALD products, depending on the customer's individual needs. ALD's ModulTherm system, for example, combines heat treatment, quenching and material handling in one. Its modular design makes it easy to adapt the system to meet particular production requirements with direct integration. Heuer believes the market has room for both the ModulTherm and SyncroTherm concepts.

"ALD's ModulTherm system consists of separate treatment chambers for low pressure carburizing (LPC) that are linked with a moving quench quench cart," he says. "The main difference is that the ModulTherm cannot be integrated into a "One-Piece-Flow" concept. It has cold walls, so it can be situated in the manufacturing building but it is fed with large batches consisting of multiple layers. We think both systems have a future and the production philosophy of the customer will dictate which system should be chosen."

Current R&D efforts besides "One-Piece-Flow" at ALD include: cycle time reductions for even bigger batches; reversing quench techniques to reduce distortion in the LPC-process (meaning alternation of the gas flow direction during the gas quench); dynamic quench techniques to reduce distortion in the LPC-process (meaning variation of the gas-speed during the gas-quench) and dry bainitizing; an austempering process performed in a high pressure gas stream instead of a salt bath.

While energy consumption is not at the top of customers' lists, it is becoming more relevant each year. "So far, unfortunately, lowering energy consumption is not a prime target for most customers, but we are sure this will change in the future," Heuer says. "Customers today, however, are already very interested in reducing the peak consumption of electricity, thus getting better pricing from their provider. ALD is offering power management software to reduce this peak consumption."

Heat treatment integrated in the production line leads to a more efficient and more ecological production of parts.

If everything goes according to plan, Heuer would like heat treat technology to become an integral part of product development and manufacturing instead of the necessary evil that it unfortunately presents to many people in the industry today. "Certainly, I'd like to see ALD as a key driver in that perspective."